If art is what humans create from the natural world around them, then the Coombes infant and nursery school has a gallery in its garden. The difference with this art gallery is that you are allowed, even encouraged, to touch the exhibits. The collection is growing all the time, and to the teachers and children - its curators and its creators - it is priceless.

When the school opened in the village of Arborfield Cross near Reading in 1971, headteacher Sue Humphries was presented with a blank canvas - two acres of grounds with a regulation patch of tarmac on its doorstep. Thirty-one years later, Ms Humphries is still the headteacher but the school is a very different place, barely recognisable from the featureless expanse seen in photographs taken soon after it opened. The tarmac is now covered with grids for playground games and surrounded by trees of all shapes, sizes and varieties, like a colourful clearing in an enchanted wood.

When Sue Humphries’s first intake of children told her they wanted trees to climb, she came up with an instant solution - old tree trunks. Easy to climb and ideal for games of hide and seek, they are still one of the playground’s most popular features. The school had to wait a generation for the real thing, but now the woods, planted over the years by pupils past and present, are mature enough to hold two tree houses - aspen lodge and pine lodge. The woods are crisscrossed by paths set with old coins and dotted with dens, hiding places and storytelling circles.

“Like a world from a story book,” says Ms Humphries. “A lot of schools make the mistake of having things done instead of getting the children involved. Then there isn’t the sense of ownership that the children here have. They have been the tree planters and they have made the pathways. It gives them something to be proud of.”

With a string of awards for its great outdoors, the Coombes school welcomes around 1,000 visitors a year. Seven-year-olds Ashley and Mark know the names of all the sheep, and the fruit and vegetables growing here and there. There are willow hedges, an amphitheatre and a mini Stonehenge, one of several outcrops of rocks scattered around the grounds donated by quarries on condition that the school pays the transport. As well as looking good, each one is a hands-on geology lesson. The school has made a virtue of its clay soil by digging it up and using it to make pottery. The cycles of life are emphasised in everything the children do. Friends of the school who have died are remembered in bridges and mulberry bushes, while vegetables, fruit trees and flowers of all kinds are just coming into bloom.

“If you have planted something, you get picker’s rights,” says Ms Humphries. “The people who come after you will also be planting things so it is constantly renewing resources. It’s a terrifically important message for the future of the world, and here the children are doing it for themselves.”

In a small clearing is an inscription from a poem by Robert Frost: “Two roads diverged in a wood and I took the one less travelled by, and that has made all the difference.” It sums up the Coombes school’s determination to go its own way. “A lot of it starts from what the children say. Like the tree house - someone said we ought to have a tree house and we just ran with the idea,” says Ms Humphries.

When a steaming pile of bark chippings was delivered, one child plunged his hand inside and remarked that it was hot enough to cook an egg. “So we did. It took three days, but we did it.”

The view from the lookout, a recently constructed timber outbuilding that doubles as an art room, is across rolling fields of barley, and it would be easy to think this is a pastoral idyll. But the M40 is just one mile away and an army garrison - where 60 per cent of the children live - and the biggest housing estate in Europe are just down the road. With imagination and effort, the Coombes school has transformed the kind of outside space many semi-rural schools have into a beautiful learning environment. It’s a place to inspire and display its children’s artistic instincts, and barely a day goes by when it isn’t used.

Ms Humphries is fond of Matisse and Georgia O’Keeffe, but the school takes inspiration from Andy Goldsworthy, famous for his outdoor ephemeral work, which ranges from large-scale land art to delicate arrangements of greenery. Having been taught the art of tessellation by fitting their shoes together on the classroom floor, Year 2 children take the technique outside, placing broken paving slabs over polythene laid out in a sunflower shape on the grass. In a few weeks’ time it will be revealed as a white outline of sun-starved turf - then turn green as the grass recovers.

Meanwhile, infants are engrossed in balancing piles of pebbles or floating twigs and leaves on the surface of water. “A lot of children say, ‘I’m no good at art’ because they can’t draw well,” says Sue Humphries. But at the Coombes school, everyone is an artist.

Ideas from the Coombes and 20 other school gardens around Britain featured in the prizewinning Growing Schools garden (see ‘Friday’ magazine, June 28) at the Hampton Court Flower Show earlier this month. This is being recreated at the Environmental Curriculum Centre, Eltham, in the London borough of Greenwich. The centre is a nine-acre wildlife site with a rich range of habitats. The charity Learning through Landscapes has its London office at the centre and the garden will be open to schools by appointment. Further information: www.thecoombes.com; www.ltl.org.uk